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Coupled Model Data Assimilation:

Coupled Model Data Assimilation:. Building an idealised coupled system Polly Smith, Amos Lawless, Alison Fowler* School of Mathematical and Physical Sciences, University of Reading, UK * funded by NERC. Outline. Recap objectives tasks & progress Progress since last meeting Next steps.

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Coupled Model Data Assimilation:

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  1. Coupled Model Data Assimilation: Building an idealised coupled system Polly Smith, Amos Lawless, Alison Fowler* School of Mathematical and Physical Sciences, University of Reading, UK * funded by NERC

  2. Outline • Recap • objectives • tasks & progress • Progress since last meeting • Next steps

  3. Objective To use an idealised system to gain a greater theoretical understanding of the coupled atmosphere-ocean data assimilation problem: • explore different approaches to coupled 4D-Var data assimilation using a single-column, coupled atmosphere-ocean model • help guide the design/ implementation of coupled DA methods within full 3D operational scale systems

  4. Building the idealised system Task 1: develop an idealised, single-column, coupled atmosphere-ocean model with a strong-constraint incremental 4D-Var assimilation scheme. The model needs to be • simple and quick to run • able to represent realistic atmosphere-ocean coupling Atmosphere: • simplified version of the ECMWF single column model (SCM) Ocean: • single column KPP (K-Profile Parameterisation) mixed-layer ocean model coupled through surface fluxes and SST

  5. Progress December 2012 • Successfully compiled and ran theSCM test-case provided by ECMWF. • Simplified the SCM code to remove physical parameterisations. • Tested the simplified atmospheric model using real data. • Coupled the KPP ocean code to the full-physics SCM and successfully ran a test case for the coupled atmosphere-ocean model. • Produced draft documentation for the models.

  6. Progress July 2013 • Revisited stripped down SCM code, now includes simplified version of the IFS turbulent diffusion scheme. • Option to run with dynamics + turbulent diffusion only dynamics + full physics (i.e. original code) • Simplified turbulent diffusion scheme computes surface fluxes to pass to ocean model. • KPP ocean code now coupled to the simplified SCM.

  7. Progress July 2013 • Produced scripts for creating coupled model input file • atmosphere data from ERA interim • ocean data from MyOcean project • Continued to update documentation for the models. • svn repository now in place. • Tangent linear and adjointmodels written and tested.

  8. Test case: 7 day run from 1stJuly 2012, (235.5oE, 24.5oN)

  9. Atmosphere

  10. ERA interim data (6 hourly)

  11. Ocean

  12. MyOcean data (daily mean)

  13. Things to think about … • Choice of suitable test-case(s) Atmosphere: • relaxation of winds Ocean: • availability of time-series data

  14. Next steps • Development of baseline 4D-Var system • minimisation algorithm • observations • error covariances • assimilation time window • Strongly coupled data assimilation experiments • aim is to have some initial results in next few months. • Exploration of different coupling strategies being implemented in the ECMWF system.

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